Endogenous cannabinoid ligands (endocannabinoids, eCBs) are produced by cells and activate cannabinoid receptors, the molecular target for marijuana's bioactive ingredient A9-tetrahydrocannabinol. Several eCBs have been indentified, including the prototypical eCB anandamide and the most abundant eCB in brain 2-arachidonoylglycerol. Yet the scientific literature is full of description of additional eCB candidates, the biosynthesis and inactivation of which remains to be elucidated. Thus it is currently particularly difficult to elucidate the involvement of a specific eCB in a given biological function because we do not know which proteins control their levels. Analysis of the yeast genome showed that many potential players in eCB biosynthesis and inactivation are conserved between yeast and higher eukaryotes. Recently we were able to unambiguously identify and quantify eCBs in Saccharomyces cerevisiae by using gas chromatography / mass spectrometry (GC/MS). An exciting feature of this result is that yeast provides an unbiased genetic tool to identify modifiers (some of which have human homologs) of biological functions, in our case eCB biosynthesis and inactivation. This R21 proposal has two specific aims: 1) identify genes that control eCB levels in yeast 2) determine if human homoloqs of these yeast genes control eCB biosynthesis and inactivation in a human neuronal cell line. Results obtained with this R21 grant will provide the basis for an RO1 aimed on understanding the genetic and molecular basis of mammalian eCB production and inactivation, a pivotal question in the field of drug of abuse research. [unreadable] [unreadable]